Methane is the second most prevalent greenhouse gas emitted in the United States as a result of human activity. Because of methane's effectiveness at trapping radiation, it is considered significantly more deleterious to the environment than carbon dioxide. Methanotrophs are gram-negative bacteria that metabolize methane and may provide routes for the remediation of the gas. In the first step of metabolizing methane, methanotrophs use an integral membrane protein called particulate methane monooxygenase (pMMO) to oxidize methane to methanol. pMMO is copper-dependent enzyme, and thus methanotrophs have an elevated requirement for copper (Cu). Under conditions of limiting Cu, some methanotrophs secrete a small natural product-like molecule that binds Cu with high affinity. This molecule, called methanobactin (Mbn), is re- internalized into the cell in its Cu-loaded form to satisfy the cell's copper needs. The proposed research will characterize the transporter implicated in the re-internalization of the Cu-Mbn complex in two different methanotrophs. This work will provide insight into the mechanism by which a key requirement for methane metabolism, the acquisition of Cu for pMMO's cofactor, is fulfilled. Additionally, it will provide insight on methanotrophic bacterial homeostasis.